Healthy Asian chicken lettuce cups

1. Mix together the ingredients for the sauce and set aside.
2. Preheat a wok or pan over medium high and add the oil, ginger, scallion whites and shiitake mushrooms; stir fry 2-3 minutes with salt and pepper.
3. Add the garlic and chicken with some more salt and pepper and stir fry until cooked through, breaking the chicken up with your spatula (3-4 min).
4. Add the water chestnuts and sauce (mix the sauce first because the cornstarch will settle) and cook until the sauce has thickened (1-2 mins).
5. Mix in the scallion greens and vinegar at the end; taste and adjust seasoning if needed.
6. Serve with iceberg lettuce and enjoy!